A number of processes and devices have been implemented to measure flow rate in different applications. Flow-through pressure sensors can be utilized in conjunction with an in-line orifice to measure very low flow rates and with reliable accuracy. Such pressure sensors have been utilized, for example, in various flow sensing devices such as medical applications, some of which utilize silicon piezoresistive sensing technology for measuring very low pressures. Other flow sensing implementations, for example, include environmental applications.
The majority of flow-through pressure sensor configurations require some type of conduit so that a pressure-sensitive component can be disposed in fluid communication with a fluid whose pressure is to be detected. The conduit can be connected to the pressure sensor utilizing a T-fitting or similar connection. Such pressure connection configurations available on most pressure sensors are ‘dead-ended’. Dead spaces affect the cleanliness of the device because any dead spaces in the conduit can trap a portion of the fluid and collect contaminants. When measuring the pressure of the fluid flowing in the conduit, dead volumes may also interfere with the smooth, laminar flow of the fluid. In high-speed dynamic applications, such tubing and fittings can limit the frequency response of the device.
Furthermore, in order to maintain extreme purity of the fluids, it has heretofore been necessary to dismantle the conduit and/or transducer manually and then clean all of the regions accessible to the fluids, which is costly and time consuming. Also, such connecting plumbing makes the measurement of a temperature of the media, or the humidity, or other characteristic of the media difficult or impossible. Such sensors have a comparatively large surface area exposed to the fluid, which can trap contaminants. It is also advantageous for a pressure sensor to be of small size. Typically, the smaller the size, the easier it is for the sensor to fit into a constricted operating environment and attach to a wide variety of sizes and shapes of conduits and containers.
Based on the foregoing, it is believed that a need exists for an improved flow-through pressure sensor apparatus with the foregoing advantages that possess a highly compact point of attachment to the conduit. A need also exits to provide a sensor with a good dynamic response.